Abstract
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A rapid influenza diagnostic test, such as a lateral flow immuno-assay (LFIA)1,2 would prove invaluable for HPAI surveillance. The hemagglutination inhibition (HI) assay or virus microneutralization (MN) assay are presently good predictors of influenza antibodies after infection. However, samples must be shipped to an appropriate MN/HI testing facility and be analyzed by trained scientists, which can be labor intensive. Presently, the lack of a rapid, cheap, point-of-care method to test humans and livestock (eg, pigs) as part of HPAI surveillance hampers epidemiologic investigations. A hand-held colorimetric LFIA used in the field, even if just qualitative, to give a quick visible yes/no answer would be highly convenient to monitor patients, medical personnel, and agriculture workers. If the LFIA test was positive, further blood could be collected and sent to a proper facility for additional MN/HI screening. There is currently little financial incentive for a biotechnology company to invest resources in an assay for a virus that is continually evolving and may not be detectable on an LFIA platform a year from now. A committed and continual investment by the national government and international agencies is therefore required to ensure that multiple LFIA prototypes are available for mass production if an HPAI pandemic event were to occur. The following 3 factors should be considered by government entities and LFIA companies when developing a simple yes/no detection system for HPAI.
1. Multiplexing (multiple hemagglutinin targets on 1 device)—The device should have multiple antigen hemagglutinin (HA) targets (ie, multiplexing) against H7 and H5 to account for potential mutation. If not multiplexed, at the very least the HA antigen testing band/spot should be validated at the prototype stage to detect more than one HPAI subtype if multiplexing is not engineered.
2. Specificity and sensitivity (limiting false-positives and false-negatives)—Animal serum collected after laboratory H5N1 and H7N9 infection can serve as an appropriate control in early steps of prototype design. However, laboratory animals are usually naïve to previous vaccinations and seasonal infection (H1, H3, B viruses) that complicate assay development by the presence of cross-reactive antibodies. Obtaining human serum from HPAI-infected patients and various uninfected humans for qualification and validation purposes is paramount to developing an effective assay. The assay should not give a false-positive for HPAI if the person has a seasonal H3N2, H1N1, or influenza B infection.
3. Simplicity—The device should be cost-effective for global distribution. Additionally, the device should be scalable for mass production if HPAI were to easily spread from human to human. Other considerations should include that the device be stable (especially against humidity), require no more than a drop of serum/blood, and not be reliant on laboratory equipment (ie, centrifuges). Finally, the device should require minimal training by a field worker or hospital staff to use on a suspected patient.
Promising developments in HPAI LFIA development have recently been reported.3,4 Investment in HPAI LFIA technology could also significantly reduce the cost of MN and HI testing at influenza laboratories by “weeding out” negative samples. It is the hope that continual investment in LFIA technology be pursued to assist in global HPAI surveillance.